ports/sh: make filesystem imports relative to current file

ports/sh/mpconfigport.h

@@ -22,6 +22,10 @@ extern const struct _mp_print_t mp_debug_print;
 #define MICROPY_DEBUG_PRINTER             (&mp_debug_print)
 #endif
 
+/* Custom option to use relative imports. For instance when working at the fs
+   root, 'import b' in '/folder/a.py' will import 'folder/b.py' not '/b.py'. */
+#define MICROPY_RELATIVE_FILE_IMPORTS     (1)
+
 /* General feature set selection
    Other options: BASIC_FEATURES, EXTRA_FEATURES, FULL_FEATURES, EVERYTHING */
 #define MICROPY_CONFIG_ROM_LEVEL (MICROPY_CONFIG_ROM_LEVEL_CORE_FEATURES)

py/builtinimport.c

@@ -444,6 +444,7 @@ STATIC mp_obj_t process_import_at_level(qstr full_mod_name, qstr level_mod_name,
             } else {
                 // No-op. Nothing to load.
                 // mp_warning("%s is imported as namespace package", vstr_str(&path));
+                DEBUG_printf("%s is imported as namespace package\n", vstr_str(path));
             }
             // Remove /__init__.py suffix.
             path->len = orig_path_len;
@@ -522,6 +523,23 @@ mp_obj_t mp_builtin___import___default(size_t n_args, const mp_obj_t *args) {
     mp_obj_t top_module_obj = MP_OBJ_NULL;
     mp_obj_t outer_module_obj = MP_OBJ_NULL;
 
+    #if MICROPY_RELATIVE_FILE_IMPORTS
+    size_t is_len;
+    mp_obj_t *is_items;
+    mp_obj_list_get(MP_STATE_VM(mp_import_stack), &is_len, &is_items);
+    if(is_len > 0) {
+        // Start next to last import
+        char const *prev = qstr_str(MP_OBJ_QSTR_VALUE(is_items[is_len - 1]));
+        char const *slash = strchr(prev, '/');
+        int prev_len = (slash ? slash : prev) - prev;
+        vstr_add_strn(&path, prev, prev_len);
+        outer_module_obj = mp_obj_new_module(MP_QSTR___blankmodule);
+        mp_store_attr(outer_module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path)));
+        DEBUG_printf("last import was '%s'\n", prev);
+        DEBUG_printf("starting in '%.*s'\n", (int)vstr_len(&path), vstr_str(&path));
+    }
+    #endif
+
     // Search for the end of each component.
     size_t current_component_start = 0;
     for (size_t i = 1; i <= module_name_len; i++) {

py/mpstate.h

@@ -176,6 +176,11 @@ typedef struct _mp_state_vm_t {
     mp_obj_dict_t *mp_module_builtins_override_dict;
     #endif
 
+    // list (stack) of nested imports for relative import resolution
+    #if MICROPY_RELATIVE_FILE_IMPORTS
+    mp_obj_t mp_import_stack;
+    #endif
+
     // Include any root pointers registered with MP_REGISTER_ROOT_POINTER().
     #ifndef NO_QSTR
     // Only include root pointer definitions when not doing qstr extraction, because

py/obj.h

@@ -1116,6 +1116,7 @@ mp_int_t mp_obj_tuple_hash(mp_obj_t self_in);
 // list
 mp_obj_t mp_obj_list_append(mp_obj_t self_in, mp_obj_t arg);
 mp_obj_t mp_obj_list_remove(mp_obj_t self_in, mp_obj_t value);
+mp_obj_t mp_obj_list_pop(mp_obj_t self_in, mp_obj_t index);
 void mp_obj_list_get(mp_obj_t self_in, size_t *len, mp_obj_t **items);
 void mp_obj_list_set_len(mp_obj_t self_in, size_t len);
 void mp_obj_list_store(mp_obj_t self_in, mp_obj_t index, mp_obj_t value);

py/objlist.c

@@ -290,6 +290,12 @@ STATIC mp_obj_t list_pop(size_t n_args, const mp_obj_t *args) {
     return ret;
 }
 
+mp_obj_t mp_obj_list_pop(mp_obj_t self_in, mp_obj_t index)
+{
+    mp_obj_t args[] = {self_in, index};
+    return list_pop(2, args);
+}
+
 STATIC void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn, mp_obj_t binop_less_result) {
     MP_STACK_CHECK();
     while (head < tail) {

py/runtime.c

@@ -119,6 +119,10 @@ void mp_init(void) {
     MP_STATE_VM(mp_module_builtins_override_dict) = NULL;
     #endif
 
+    #if MICROPY_RELATIVE_FILE_IMPORTS
+    MP_STATE_VM(mp_import_stack) = mp_obj_new_list(0, NULL);
+    #endif
+
     #if MICROPY_PERSISTENT_CODE_TRACK_RELOC_CODE
     MP_STATE_VM(track_reloc_code_list) = MP_OBJ_NULL;
     #endif
@@ -1585,13 +1589,28 @@ mp_obj_t mp_parse_compile_execute(mp_lexer_t *lex, mp_parse_input_kind_t parse_i
     mp_globals_set(globals);
     mp_locals_set(locals);
 
+    #if MICROPY_RELATIVE_FILE_IMPORTS
+    char const *volatile name = qstr_str(lex->source_name);
+    (void)name;
+    if (parse_input_kind == MP_PARSE_FILE_INPUT) {
+        mp_obj_list_append(MP_STATE_VM(mp_import_stack), MP_OBJ_NEW_QSTR(lex->source_name));
+        #if DEBUG_PRINT
+        DEBUG_printf("pushing import: ", name);
+        mp_obj_print_helper(MICROPY_DEBUG_PRINTER, MP_STATE_VM(mp_import_stack), PRINT_REPR);
+        DEBUG_printf("\n");
+        #endif
+    }
+    #endif
+
     nlr_buf_t nlr;
+    bool volatile failed = false;
+    mp_obj_t volatile ret;
+
     if (nlr_push(&nlr) == 0) {
         qstr source_name = lex->source_name;
         mp_parse_tree_t parse_tree = mp_parse(lex, parse_input_kind);
         mp_obj_t module_fun = mp_compile(&parse_tree, source_name, parse_input_kind == MP_PARSE_SINGLE_INPUT);
 
-        mp_obj_t ret;
         if (MICROPY_PY_BUILTINS_COMPILE && globals == NULL) {
             // for compile only, return value is the module function
             ret = module_fun;
@@ -1604,13 +1623,27 @@ mp_obj_t mp_parse_compile_execute(mp_lexer_t *lex, mp_parse_input_kind_t parse_i
         nlr_pop();
         mp_globals_set(old_globals);
         mp_locals_set(old_locals);
-        return ret;
     } else {
         // exception; restore context and re-raise same exception
         mp_globals_set(old_globals);
         mp_locals_set(old_locals);
-        nlr_jump(nlr.ret_val);
+        failed = true;
     }
+
+    #if MICROPY_RELATIVE_FILE_IMPORTS
+    if (parse_input_kind == MP_PARSE_FILE_INPUT) {
+        mp_obj_list_pop(MP_STATE_VM(mp_import_stack), MP_OBJ_NEW_SMALL_INT(-1));
+        #if DEBUG_PRINT
+        DEBUG_printf("popping import: ", name);
+        mp_obj_print_helper(MICROPY_DEBUG_PRINTER, MP_STATE_VM(mp_import_stack), PRINT_REPR);
+        DEBUG_printf("\n");
+        #endif
+    }
+    #endif
+
+    if(failed)
+        nlr_jump(nlr.ret_val);
+    return ret;
 }
 
 #endif // MICROPY_ENABLE_COMPILER